1. Field of the Invention
This invention relates to a light beam recording apparatus for recording an image by deflecting a light beam modulated on the basis of image information and scanning the light on a recording surface, a light beam read-out apparatus for reading out an image such as a radiation image, and a light beam scanning apparatus for scanning a light beam with a light deflector. This invention particularly relates to a light beam recording apparatus, a light beam read-out apparatus, and a light beam scanning apparatus which have a small size and may be manufactured with a low cost.
2. Description of the Prior Art
Various light beam recording apparatuses have heretofore been proposed for modulating a light beam emitted by a light beam source on the basis of image information, and two-dimensionally scanning the modulated light beam on a recording material by use of a light beam scanning apparatus, thereby recording an image on the recording material. The light beam recording apparatus of this type is connected, for example, to a radiation image read-out apparatus as proposed by the applicant for scanning a stimulable phosphor sheet carrying a radiation image stored thereon with stimulating rays and photoelectrically detecting the image to generate an image signal, and is used for obtaining a hard copy having an improved image quality, particularly a high diagnostic efficiency and accuracy, based on the image signal.
In the aforesaid light beam recording apparatus, two-dimensional light beam scanning by the light beam scanning apparatus is conducted by deflecting the light beam with a light deflector so that the light beam scans the recording material in a main scanning direction, and at the same time moving the recording material with respect to the light beam in a sub-scanning direction approximately normal to the main scanning direction. However, the conventional apparatus has the drawbacks that the apparatus becomes large and expensive because of the means for conducting the scanning in the sub-scanning direction. FIG. 50 is a schematic perspective view showing the conventional light beam recording apparatus. Drawbacks of the conventional light beam recording apparatus will hereinbelow be described with reference to FIG. 50.
In FIG. 50, a light beam 102 emitted by a light beam source 101 is made to impinge upon a modulator 103 operated by a modulator drive circuit 104, and is modulated with a signal generated by an image signal output device 105. Then, the light beam 102 is made to impinge upon a multi-face rotating mirror 106 acting as a light deflector, and is reflected and deflected thereby as the multi-face rotating mirror 106 rotates in the direction as indicated by the arrow A. The light beam 102 reflected by the multi-face rotating mirror 106 passes through an f.theta. lens 107 provided in the optical path as an image forming lens, and scans a recording sheet 108 in the main scanning direction as indicated by the arrow B. The recording sheet 108 is held between a rotatable drum 109 for rotation in the direction as indicated by the arrow C and a pair of rollers 110A and 110B provided on the rotatable drum 109. As the rotatable drum 109 rotates, the recording sheet 108 is conveyed in the sub-scanning direction as indicated by the arrow D approximately normal to the main scanning direction. Thus the recording sheet 108 conveyed in the sub-scanning direction as indicated by the arrow D is repeatedly scanned by the light beam 102 in the main scanning direction as indicated by the arrow B. Therefore, the recording sheet 108 is scanned two-dimensionally, and an image is recorded approximately over the whole surface of the recording sheet 108.
In the aforesaid light beam recording apparatus, scanning in the sub-scanning direction is conducted by moving the recording sheet 108. However, in order to prevent sub-scanning nonuniformity by minimizing fluctuations in load to a motor 113 during the sub-scanning, it is necessary to provide a space for accommodating one recording sheet 108 at the front and rear of the scanning position of the light beam 102, for example, by providing supporting bases 111 and 112 for supporting the recording sheet 108. Therefore, in the aforesaid light beam recording apparatus, it is necessary to provide a space having a length equal to the sum of the lengths of two recording sheets 108 or more in the sub-scanning direction, and the apparatus becomes large. Also, in order to convey the recording sheet 108 consistently, the rotatable drum 109 for conveying the recording sheet 108 should have a width larger than the width of the recording sheet 108. Further, since the motor 113 for rotating the rotatable drum 109 is provided in the width direction of the rotatable drum 109, the aforesaid apparatus becomes large also in the main scanning direction.
Also, in order to record accurately on the recording sheet 108 which the recording sheet 108 is conveyed, it is necessary to control the motor 113 accurately so that the recording sheet 108 may be accurately conveyed at a predetermined speed in the correct direction. However, since the accurately controllable motor is expensive, the cost of the whole apparatus becomes markedly high. Further, the rollers 110A and 110B are essential to convey the recording sheet 108 consistently. However, when the rollers 110A and 110B are provided, recording cannot be achieved at two end portions of the recording sheet 108 in the sub-scanning direction, and a need for recording the two end portions as black edges or the like cannot be satisfied.
On the other hand, there have also been widely used image read-out apparatuses wherein an image recorded on a sheet is read out by two-dimensionally scanning the sheet with a light beam such as a laser beam, and detecting light carrying the image information obtained by exposure of the sheet to the light beam, such as light reflected by the sheet, light transmitting through the sheet, or light emitted by the sheet, by use of a light detection means provided with a photomultiplier or the like.
The image read-out apparatus of this type is used, for example, as a scanner for plate making, an input apparatus for a computer or a facsimile, and a radiation image read-out apparatus in a radiation image recording and reproducing system using a stimulable phosphor sheet as disclosed, for example, in U.S. Pat. Nos. 4,258,264 and 4,346,295, and Japanese Unexamined Patent Publication No. 56(1981)-11395.
Specifically, when certain kinds of phosphors are exposed to a radiation such as X-rays, .alpha.-rays, .beta.-rays .gamma.-rays, cathode rays or ultraviolet rays, they store a part of the energy of the radiation. Then, when the phosphor which has been exposed to the radiation is exposed to stimulating rays such as visible light, light is emitted by the phosphor in proportion to the stored energy of the radiation. A phosphor exhibiting such properties is referred to as a stimulable phosphor. In the aforesaid radiation image read-out apparatus, a radiation image of an object such as the human body is stored on a sheet provided with the stimulable phosphor, the stimulable phosphor sheet carrying the radiation image stored thereon is then scanned with stimulating rays such as a laser beam which cause the sheet to emit light in proportion to the stored energy of the radiation, and the emitted light is photoelectrically detected to obtain an image signal.
In the light beam read-out apparatus as mentioned above, two-dimensional light beam scanning is conducted as described above. However, the apparatus has the drawbacks that the apparatus becomes large because of the sub-scanning means and the optical system is complicated and expensive. FIG. 51 is a perspective view showing an example of the conventional light beam read-out apparatus, and FIG. 52 is a side view showing another example thereof. Drawbacks of the conventional light beam read-out apparatus will hereinbelow be described with reference to FIGS. 51 and 52.
In FIG. 51, the light beam read-out apparatus is constituted as a radiation image read-out apparatus. Stimulating rays 122 of a predetermined intensity emitted by a stimulating ray source 121 are made to impinge upon a galvanometer mirror 123 acting as a light deflector, and are reflected and deflected thereby as the galvanometer mirror 123 rotates in the direction as indicated by the arrow A. The stimulating rays 122 deflected by the galavanometer mirror 123 pass through an f.theta. lens 124 provided in the optical path as an image forming lens, and then scan a stimulable phosphor sheet 105 both ways in the main scanning direction as indicated by the arrow B. While the stimulating rays 122 impinge upon the stimulable phosphor sheet 105, the sheet 105 is conveyed by an endless belt device 126 in the sub-scanning direction as indicated by the arrow D approximately normal to the main scanning direction. Therefore, the stimulable phosphor sheet 105 is two-dimensionally scanned over the whole surface by the stimulating rays 122 through the deflection of the stimulating rays 122 conducted by the galvanometer mirror 123 and the conveyance of the stimulable phosphor sheet 105 conducted by the endless belt device 126.
As the stimulable phosphor sheet 105 is scanned by the stimulating rays 122, the portion of the sheet 105 exposed to the stimulating rays 122 emits light in proportion to the stored radiation energy. The light emitted by the stimulable phosphor sheet 105 enters a transparent light guide member 127 from its light input face 127a positioned close to the sheet 105 in parallel to the main scanning line. The light guide member 127 has a flat-shaped front end portion 127b positioned close to the stimulable phosphor sheet 105 and is shaped gradually into a cylindrical shape towards the rear end side to form an approximately cylindrical rear end portion 127c which is closely contacted with a photomultiplier 128. The light emitted by the stimulable phosphor sheet 105 upon stimulation thereof and entering the light guide member 127 from its light input face 127a is guided inside of the light guide member 127 up to the rear end portion 127c, and received by the photomultiplier 128 via a filter (not shown) for selectively transmitting the light emitted by the stimulable phosphor sheet 105. Thus the light emitted by the stimulable phosphor sheet 105 in proportion to the stored radiation energy is detected and converted into an electric image signal by the photomultiplier 128. The electric image signal thus obtained is sent to an image processing circuit 129 and processed therein. The electric image signal thus processed is then reproduced into a visible image and displayed, for example, on a cathode ray tube (CRT) 130, or stored on a magnetic tape 131, or directly reproduced as a hard copy on a photographic film or the like.
However, in the aforesaid radiation image read-out apparatus, since the sub-scanning is conducted by moving the stimulable phosphor sheet 105, it is necessary for the endless belt device 126 to have such a size that one stimulable phosphor sheet 105 may be placed at the front and rear of the scanning position of the stimulating rays 122 as shown. Therefore, the endless belt device 126 should have a length at least equal to the sum of the lengths of two stimulable phosphor sheets in the sub-scanning direction, and the apparatus becomes large as a whole.
In the radiation image read-out conducted by use of the aforesaid radiation image read-out apparatus, preliminary read-out may be carried out for ascertaining the radiation image stored on the stimulable phosphor sheet 105 prior to final read-out for obtaining the image signal used for reproducing a visible image, and read-out conditions in the final read-out or the like may be adjusted based on the image information obtained by the preliminary read-out, and the final read-out may be carried out by use of the read-out conditions.
One method of conducting the aforesaid preliminary read-out is disclosed, for example, in Japanese Unexamined Patent Publication No. 58(1983)-67240. In the disclosed method, the stimulable phosphor sheet 105 is scanned with the stimulating rays of a level lower than the stimulating rays used in the final read-out, and light emitted by the stimulable phosphor sheet 105 during the scanning is detected by use of a photoelectric read-out means.
In order to conduct the preliminary read-out and the final read-out continuously, the preliminary read-out is first conducted by conveying the stimulable phosphor sheet 105 in the direction as indicated by the arrow D, and then the endless belt device 126 is rotated reversely to return the stimulable phosphor sheet 105 in the direction as indicated by the arrow D' to the read-out starting position. Thereafter, the final read-out is carried out by conveying the stimulable phosphor sheet 105 in the direction as indicated by the arrow D. Or, the preliminary read-out is conducted by conveying the stimulable phosphor sheet 105 in the direction as indicated by the arrow D, the final read-out is carried out by returning the sheet 105 in the direction as indicated by the arrow D', and then the sheet 105 is conveyed in the direction as indicated by the arrow D out of the read-out apparatus. However, in any case, since the time is required for conveying the stimulable phosphor sheet 105 and changing the position thereof, the time required for the preliminary read-out and the final read-out becomes long, and the read-out cannot be conducted efficiently. Further, in another example of the conventional radiation image read-out apparatus shown in FIG. 52, a stimulating ray source 121A for preliminary readout and a stimulating ray source 121B for final read-out are provided in the read-out apparatus, a stimulable phosphor sheet is conveyed in the direction as indicated by the arrow E by a conveyance means comprising endless belt devices 129A, 129B, 129C, 129D and 129E, and the preliminary read-out and the final read-out are conducted sequentially without conveying the stimulable phosphor sheet reversely. However, in this apparatus, the conveyance means having a length at least equal to the sum of the lengths of three stimulable phosphor sheets in the sub-scanning direction is necessary for conducting the preliminary read-out and the final read-out on the stimulable phosphor sheet. Further, two photoelectric read-out means are necessary for the preliminary read-out and the final read-out. Therefore, the apparatus becomes very large and expensive.
Also, with the conventional light beam read-out apparatuses shown in FIGS. 51 and 52, since read-out should be effected accurately while the stimulable phosphor sheet is conveyed, it is necessary to convey the stimulable phosphor sheet accurately at a predetermined speed in the correct direction by the conveyance means such as the endless belt device. Therefore, a motor or the like for operating the conveyance means must be controlled accurately so that the conveyance means operates consistently even though load fluctuations arise during movement of the stimulable phosphor sheet. However, since the accurately controllable motor is expensive, the cost of the apparatus as a whole becomes markedly high.